Process for the preparation of a silica-group vill metal oxide catalyst



E. A. HUNTER EI'AL 2,472,833 PROCESS FOR THE PREPARATION OF A SILICA-GROUP VIII METAL OXIDE CATALYST Filed Feb. 28, 1947 June 14, 1949.

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Patented June 14, 1949 PROCESS FOR THE PREPARATION OF A SILICA-GROUP VIII METAL OXIDE CATA- LYST Edward A. Hunter and Charles N. Kimberlin, in, Baton Rouge, La... minors to Standard Oil Development Company, a corporation of Dela- Application February 28, 1947, Serial No. 731,564

14 Claims.

Our invention is concerned with improved catalysts and more specifically relates to an improved process for the preparation of catalysts suitable for utilization in cracking, reforming, isomerization, polymerization and alkylation processes. Our invention is particularly concerned with an improved method for the preparation of catalyst comprising silica. In accordance I with our invention, catalysts comprising silica are prepared by treating a silica-magnesia hydrogel with a metal salt solution under conditions to produce a catalyst comprising. silica and the oxide of the metal. In accordance with our process the salt soluton is a salt solution of a metalselected from group 8 of the periodic table.

It is well known in the art to improve the quality of oils, particularly petroleum oils, by treating the same with catalyst under various operating conditions. For example, it is known to treat high-boiling petroleum oils with a catalyst comprising silica at temperatures in the range from about 600 F. to about 1100 F. in order to crack the oil and to secure petroleum oil fractions boiling in the motor fuel boiling range. Oxides of other metals, as for example, magnesium, manganese, zirconium, beryllium and aluminum are employed in conjunction with the silica. Particularly desirable catalysts suitable for treating petroleum oils in order to hydrogenate or dehydrogenate the 011 comprises a silica-iron, a silicacobalt or a silica-nickel catalyst.

Heretofore these catalysts have been prepared by various procedures. One method is to prepare the silica hydrogel by mixing an alkali silicate with an acid. The alkali silicate usually comprises a sodium silicate (Na2O.3.25SiOa) solution having a specific gravity of about 1.2. This is mixed with a sulfuric acid having a specific gravity somewhere in the range of about 1.19. The silica hydrosol .may be impregnated with a soluble salt of the desired metal or the silica hydrosol may be allowed to gel and the resulting silica hydrogel washed and soaked in a solution comprising the salt of the desired metalor metals. One method employed, for the preparation of a silica magnesia, catalyst is to prepare the byalyst is dried at a temperature in the range from about 200 F. to 270 F. Another method utilized for the preparationv of the silica-magnesia catalyst is to prepare the. silica hydrogel by mixing sulfuric acid and alkali metal silicate. The silica hydrogel is washed and impregnated with magnesium sulfate. The impregnated silica hydrogel is treated with an ammonia solution to precipitate the magnesia. This may require a time period of from about 8 to '24 hours. A preferred method of preparing a catalyst comprising silica and magnesia is to add magnesia to a silica hydrosol or tea silica hydrosol impregnated with a metal salt such as with an aluminum salt. The mixture is washed preferably at elevated temperatures. The general process comprises adding magnesia preferably as a slurry in water to a silica hydrosol which has been impregnated with a salt, as for example, with an aluminum salt.

' The action of magnesia is to neutralize the free acid, thus causing rapid setting of the hydrosol to the hydrogel and also to decompose the aluminum salt or other salt present causing precipitation of alumina within and throughout'th'e gel.

' Excess magnesia used over these requirements remains in the finished product as magnesia. The magnesia employed to neutralize the acid and the salt of the added third metal, reacts to form magnesium salt which is removed upon washing. If it is desired to produce a gel comprising silica and magnesia, excess magnesia is added preferably as a water slurry over that required to neudrogel by the mixing of a silicate and sulfuric acid. The hydrogel is washed and mixed and granulated with magnesia and water. The mixture is passed through a colloid mill and homogenized. 'The catalyst is aged at room' temperatralize the excess acidity thus causing the formation of a gel comprising silica and'magnesia.

We have now discovered an "improved process for the preparation of a catalyst gel comprising silica and a metal oxide the metal of which is selected from group 8 of the periodic table. Our process comprises preparing a hydrogel of silica and magnesia. This is prepared by any suit- .able means, preferably by preparing a silica hydrosol by the mixing of a sodium silicate with an acid preferably sulfuric acid. The silica hydrosol is treated with magnesia preferably with a water slurry of magnesia and gelled to form a gel comprising silica and magnesia. The resulting gel is then treated with a solution of a metal salt the metal ofwhich is selected from group 8 ture for a period from about 24 to '12 hours. Elevated temperatures have also been employed in which cases, the aging time period is reduced to a period of from about 5 to 10 hours. The catcomprising silica and a metal oxide.

The process of our invention may be readily understood by reference to the drawing illustrating an embodiment of the same.

Referring specifically to the drawing a silica sol is prepared by withdrawing sulfuric acid from zone Ill by means of line I and mixing the acid with sodium silicate which is withdrawn from zone 20 by means of line 2. The mixtures pass through line 3; A water slurry of magnesia is withdrawn from zone 3|! and introduced into line 3 by means of line 4. The mixture is then passed through a spray nozzle arrangement Ill. Nozzle arrangement 40 may comprise a rotating or equivalent spray means. The material passing from means 40 comprises a silica magnesia sol which sets rapidly to a silica magnesia gel. The gel particles fall downwardly through zone 50 which preferably comprises air. It is to be understood however that zone Ill may contain oil or another water immiscible fluid.

In accordance with our invention a metal salt solution is withdrawn from zone and introduced in the bottom of zone 80 by pumping or equivalent means 5. For the purpose of illustration it is assumed that the metal salt solution comprises a metal sulfate solution. In the bottom of zone 50 the magnesia of the gel is replaced by the metal oxide of the metal salt resulting in a gel comprising silica and metal oxide.

The solution is withdrawn from zone 50 by means of line 6 and passed through a separation and washing zone 10. The filtrate comprising a metal sulfate solution is withdrawn from zone 10 by means of line l and is preferably recycled by means of line 9. This solution however may be partially or wholly withdrawn from the system by means of line H. The solids after removal of the filtrate comprise gel particles consisting of silica and metal oxide. The solids also comprise magnesium and sodium sulfates. The magnesium and sodium sulfate are removed by washing the solids with water which is introduced into zone by means of line I. The water containing dissolved magnesium and sodium sulfate is removed from zone 10 by means of line 8.

The washed silica gel comprising silica and metal oxide is withdrawn from zone 10 by means of line I2 and passed into a drying zone 80. Here the gel is dried or heat treated at the desired temperature for any desirable period of time. The dried or heat treated gel is withdrawn from zone 80 and passed to storage zone 90 and handled in any manner desirable.

The process in our invention comprises preparing a silica-magnesia hydrogel by any suitable process. The resulting hydrogel is then preferably sprayed into a solution of the metal salt. Any salt solution which is characterized by the fact that the metal of the salt will form the oxide and replace the magnesia in the silica-magnesia hydrogel is satisfactory. The chlorides, the sulfates and the nitrates may be used. However it is preferred to use the sulfates of the metals of group 8 of theperiodic table. This catalyst is washed to remove the magnesium sulfate and also any sodium sulfate present. The catalyst is then dried and activated as desired.

The process may be somewhat modified, for example, the silica-magnesia hydrogel may be washed with water to remove magnesium sulfate and sodium sulfate prior to soaking the silicamagnesia hydrogel in the metal salt solution. Although we prefer to use room temperatures, in the soaking operation it is to be also understood that elevated temperatures and higher pressures may be employed.

By preparing the silica metal oxide hydrogel in accordance with our process. it is possible to get a hydrogel comprising a relatively high percentage of the metal oxide.

The process of our invention is not to be limited by any theory as to mode of operation but only in and by the following claims in which it is desired to claim all novelty insofar as the prior art permits.

We claim:

1. Improved process for the preparation of a hydrogel comprising silica and an oxide of a metal of group 8 of the periodic table which comprises admixing a silica sol and an aqueous slurry of magnesia, converting the resulting mixture to a silica-magnesia hydrogen, contacting said hydrogel with a solution of a salt of a metal selected from group 8 of the periodic table for a sumcient period of time to permit the mangesia of the hydrogel to react with the said metal salt to form, by double decomposition, a silica-metal oxide hydrogel and a magnesium salt, and washing the silica-metal oxide hydrogel free of the magnesium salt.

2. Process as defined by claim 1 wherein said metal salt solution is a sulfate solution.

3. Improved process for the preparation of a hydrogel comprising silica and an oxide of a metal of group 8 of the periodic table which comprises spraying a mixture of a silica sol and an aqueous slurry of magnesia into a zone wherein the sprayed mixture is converted to particles of silica-magnesia hydrogel, contacting the said hydrogel particles in said zone with a solution of a salt of a metal selected from group 8 of the periodic table for a suflicient period of time to permit the magnesia of the silica-magnesia hydrogel to react with the metal salt to form a hydrogel of silica and of the oxide of the metal selected and a magnesium salt, and washing the silica-metal oxide hydrogel free of the magnesium salt.

4. Improved process for the preparation of a hydrogel comprising silica and a metal of group 8 of the periodic table which comprises preparing a silica-magnesia hydrogel. soaking said hydrogel in a solution of asalt of a metal selected from group 8 of the periodic table, maintaining said hydrogel in contact with the metal salt solution for a sumcient period oftime to cause the magnesia of the hydrogel to react with the metal salt to form a silica-metal oxide hydrogel and a magnesium salt and washing the silica-metal oxide hydrogel free of um salt.

5. Improved process for the preparation of a hydrogel comprising silica and a metal of group 8 of the periodic table which comprises spraying a. mixture of a silica sol and an aqueous slurry of magnesia into an initial zone wherein the sprayed mixture is converted to particles of sillea-magnesia hydrogel, contacting said hydrogel particles in a portion of said zone with a solution of the salt of a metal selected from group 8 of the periodic table for a suflicient period of time to cause the magnesia of the hydrogel to react with the metal salt to form a magnesium salt and a silica-metal oxide hydrogel, withdrawing the resulting mixture of silica-metal oxide hydrogel, metal salt solution and um salt from said initial zone and the same to a second zone, separating the solids from the mixture by filtration in said second zone, recycling the resulting filtrate to said initial none, washing the separated solidsinsaidsecondzone with water to dissolve out magnesium salt from the solids, removing the washed silica-metal oxide hydrogel from said second zone and passing said washed hydrogeltoadryingzoneandrecoveringdried hydrogel from said drying zone.

6. Process as defined by claim 8, wherein said metal-salt solution comprises an iron salt.

7. Process as defined by claim 3, wherein said metal salt solution comprises a cobalt salt.

8. Process as defined by claim 3 wherein said metal salt solution comprises a nickel salt.

9. Process as defined by claim 4, wherein said metal salt solution comprises an iron salt.

10. Process as defined by claim 4, wherein said metal salt solution comprises a cobalt salt.

11. Process as defined by claim 4, wherein said metal salt solution comprises a nickel salt.

12. Process as defined by claim 5 wherein said metal salt solution comprises an iron salt.

18. Process as defined by claim 5 wherein said metal salt solution comprises a cobalt salt.

14. Process as defined by claim 5 wherein said metal salt solution comprises a nickel salt.

' EDWARD A. HUNTER.

CHARLES N. KIMBERLIN, JR.

asraaancss crrsn The following references are of record in the tile of this patent:

UNITED STATES PATENTS 

